1. Field of the Invention
The present invention relates to a sheet processing apparatus comprising a stapler which binds a sheet stack with a staple and cuts off an excess part of the staple, an image forming apparatus, a control method, and a program.
2. Description of the Related Art
There is conventionally available a sheet binding apparatus which is configured to bind a sheet stack at an arbitrary position of an edge of the sheet stack by moving a binding mechanism portion (stapler) along the sheet stack aligned on a loading tray on which sheets are loaded.
Examples of a sheet binding apparatus annexed to an image forming apparatus such as a copier include one which performs the following processing. More specifically, the sheet binding apparatus conveys sheets bearing toner images formed by an image forming portion of the image forming apparatus to a loading tray, aligns a predetermined number of ones of the sheets, moves a stapler to a predetermined position of an edge of the sheet stack aligned on the loading tray, and performs binding.
There is also proposed a stapler described in Japanese Patent No. 03,541,273. When there are a large number of materials to be bound (sheets) on a binding table, a staple with long legs is used. If a small number of materials to be bound are bound with a staple with long legs, the two legs of the staple overlap each other at the time of bending the legs. To prevent this, there is known a stapler comprising a mechanism which cuts off a part, other than a part necessary for binding, of each of the legs of a staple extending through materials to be bound on a binding table and projecting from the back of the materials to be bound and clinches the staple. In a stapler of this type, partial staple legs cut off are accumulated in a containing box provided to the stapler.
However, if the stapler described in Japanese Patent No. 03,541,273 is applied to the above-described sheet binding apparatus, the following problem occurs. More specifically, if consecutive staple jobs (the jobs of binding a sheet stack) are executed, partial staple legs cut off by the stapler are accumulated in the containing box provided to the stapler. Sooner or later, the containing box is filled with partial staple legs, and as a result, some of the partial staple legs overflow the containing box and scatter in a sheet processing apparatus, which is a problem.